Experiments are designed to use mouse teratoma cells as source material for analysis of events of cellular differentiation. Teratoma cells, demonstrated to be multipotential, will be studied with an aim of directing differentiation along specific pathways by appropriate use of inductive environments. Tissue culture and transplantation techniques will be utilized. Clonal lines will be developed with the hope of obtaining a series of variants with partial developmental restrictions. Cytogenetic studies will be initiated and the work will be expanded to use of teratoma material from clinical sources.